Liquid crystalline organic compound, organic semiconductor structure, organic semiconductor device, and process for producing liquid crystalline organic compound

Abstract

A liquid crystalline organic compound which gives a liquid crystal phase in a temperature range containing at least a room temperature and can exhibit a high charge mobility; an organic semiconductor structure and an organic semiconductor device each having the liquid crystalline organic compound are provided. The liquid crystalline organic compound contains any one of benzothiazole, benzoselenazole, benzoxazole and indene skeletons represented by the following chemical formula 1: wherein A is a nitrogen atom or a CH group, and B is a sulfur, selenium or oxygen atom is contained as Z1 in the following chemical formula 2: R1-Y1-Z1-Y2-R2   2 wherein, R1 and R2 are each independently a saturated or unsaturated hydrocarbon of a straight chain, a branched chain or a cyclic structure having 1 to 22 carbon atoms; R1 and R2 may be each independently bonded directly to Z1 without interposing Y1 or Y2 therebetween; and Y1 and Y2 are each independently selected from the group consisting of oxygen and selenium atoms and —CO—, —OCO—, —COO—, —N═CH—, —CONH—, —NH—, —NHCOO and —CH2 groups.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystalline organic compound which gives a liquid crystal phase in a temperature range containing at least a room temperature and can exhibit a high charge mobility; an organic semiconductor structure and an organic semiconductor device each having the liquid crystalline organic compound; and a process for producing a liquid crystalline organic compound. The invention relates in particular to a liquid crystalline organic compound that can be continuously produced with uniform performances over a sufficiently wide area; and others. [0003] 2. Description of the Related Art [0004] Conventionally, as liquid crystalline organic compounds, ones having various structures have been known, and have widely been used mainly as materials for liquid crystal displays. A typical example of an element constituting an organic semiconductor device is a thin film transistor (may also be referr...

AI Technical Summary

Benefits of technology

[0013] The liquid crystalline organic compound of this aspect gives a liquid crystal phase in a wide temperature range containing at least a room temperature and can exhibit a high charge mobility.

[0015] The liquid crystalline organic compound of this aspect gives a liquid crystal phase in a wide temperature range containing at least a room temperature and can exhibit a high charge mobility.

[0022] According to this aspect, impurities, which are causes of a fall in the charge mobility, can be effectively removed since the synthesized crude liquid crystalline organic compound is purified by the recrystallization method using at least two kinds of solvents selected from a protonic polar solvent, an aprotonic polar solvent, a basic solvent, a halogenated hydrocarbon solvent, and a nonpolar solvent.

[0025] According to the process for producing a liquid crystalline organic compound of the invention, impurities, which are causes of a fall in the charge mobility, can be effectively removed. Therefore, the liquid crystal compound, which gives a liquid crystal phase in a temperature range containing at least a room temperature and can exhibit a high charge mobility, can be effectively produced.

Problems solved by technology

However, the organic semiconductor layer formed by the above-mentioned vacuum film-formation generally exhibits a polycrystalline state that microcrystals gather, and thus a large number of grain boundaries are liable to be present.

Moreover, defects are easily generated.

The grain boundaries or defects hinder the transportation of charges.

Accordingly, in the case of forming an organic semiconductor layer, which is an element constituting an organic semiconductor device, by the vacuum film-formation, it is in reality difficult to form the organic semiconductor layer continuously with uniform performances over a sufficiently wide area.

However, in this discotic liquid crystal, a charge is transported based on an one-dimensional charge transporting mechanism along the columnar molecular alignment thereof; therefore, strict control over the molecular alignment is required so as to cause a problem that the liquid crystal is not industrially used at ease.

However, there are problems such that when the 6-position of phenylbenzothiazole is brominated in the stage of a synthesis route of the phenylbenzothiazole derivative, the 3′-position of the phenylbenzothiazole derivative is also brominated so that the derivative is not easily purified; a sulfur atom is interposed as a spacer moiety between the core and the terminal of the structure thereof but the carbon-sulfur bond is easily oxidized and is not necessarily chemically stable; and the temperature range for keeping the state of liquid crystal is a narrow range of 90 to 100° C. Thus, a successful example of a thin film transistor in which a rodlike liquid crystalline material is used in an organic semiconductor layer has not yet been reported.

Thus, there are restrictions for the production of a device therefor.

Furthermore, the temperature at which the rodlike liquid crystalline material exhibits a high liquid crystal property is a relatively high temperature, and thus the rodlike liquid crystalline material cannot be used at liquid-crystal-state keeping temperatures which contain a temperature of around a room temperature.

However, the formed organic semiconductor layer has a low charge mobility of 1.0×10−5 to 1.0×10−6 cm2 / V·s and further there remain problems that the mobility has the temperature dependency or the electric field dependency.

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